Matt Mets is making an infrared camera intervalometer for his Nikon camera. Lucky for us, he’s also an electrical engineer, and explains things very well. He writes:

An intervalometer is a device that sends out a signal at regular intervals. When hooked up to a camera, they can be used to take time lapse images, bracket exposure lengths and precisely time long exposure images (over 30 seconds) that the built-in timer on the camera cannot normally generate. When hooked up to a flash, they can be used to create a strobe effect. Being this useful, there are many different DIY projects to make them. Unfortunately, most of them work by triggering an electronic cable release, which my Nikon D40 and N75 happen to lack. Luckily, though, both of these cameras do sport a nice infrared control port. This brings us to this project- an infrared remote intervalometer. Todays portion of the project is to get the microcontroller to talk to the camera.